Deck support for abrading tool



June 17, 1969 J. M. suoDARTH DECK SUPPORT FOR ABRADING TOOL Filed .July22, 196s ora Sheet /8 L /a2 RRloR ART PRIOR` ART F/ G' 3 Rm mp. M NM R of WU m 5 M. Y M

June 17,' l969 J. M; suDoARTH 3,449,865

DECK SUPPORT FOR ABRADING TOOL Filed July 22, 1966 sheet 2 of 2 /NvE/vron JACK M. SUDDARTH BY ATT RNEYS United States Patent O 3,449,865DECK SUPPORT FOR ABRADING TOOL Jack M. Suddarth, Muskogee, Okla.,assignor to Coburn Manufacturing Company, Inc., Muskogee, Okla., acorporation of Oklahoma v Filed July 22, 1966, Ser. No. 567,132

Int. Cl. B24b 7/00, 9/00 U.S. Cl. 51-55 1 Claim ABSTRACT OF THEDISCLOSURE A supporting assembly for the abrading cup of a lensgenerator of a type having a pivotal rst deck wherein an additional deckis provided which is pivotal about the same axis as said first deck andpivotal with respect thereto whereby the cup can be positioned to grindboth convex and concave curves without disturbing the built-inorientation between the axis about which the decks pivot and theabrading edge of the cup.

This invention relates to an improved lens generator of the typedesigned to grind both the concave and convex curves on an ophthalmiclens blank. In particu-lar, the generator of this invention provides anoperating assembly whereby the grinding edge of an abrading tool doesnot require re-orientation upon a changeover from convex to concavegrindings.

The improvement of this invention is in that type generator utilizing arotating grinding cup as the grinding element. In this type of machine,the grinding edge of the abrading tool must be located accurately withrespect to the lens blank so that as the grinding tool traverses thelens blank, the proper prescription surfaces are formed on the lensblank. In the prior art devices, when switching from positive tonegative surfacees the quill or the abrading tool supporting structureis normally moved from side to side on its supporting deck whereby asthe grinding sweep is made, a different edge of the grinding tool ispresented to the lens blank. In the instant invention, structure isprovided to eliminate this sliding by including a separate pivoting deckfor the quill or supporting tool assembly. Therefore, another objectiveof this invention is to provide a means whereby a lens generator iseasily adapted for grinding both convex and concave curves without majoradjustments being made to the sweep mechanism.

A still further objective of this invention is to provide a lensgenerator wherein the direction of sweep is opposite for plus and minuscuttings.

These and other objects of the invention will become more apparent upona reading of the following speciications taken together with theattached drawings in which:

FIGURES 1 and 2 are diagrammatic, horizontal plan views of the abradingsweep supporting structure of the prior art;

FIGURE 3 is a diagrammatic elevational view of the structure shown inFIGURES 1 and 2;

FIGURE 4 is a diagrammatic horizontal plan of the invention of thisdisclosure showing the disposition of parts as a minus curve isgenerated;

FIGURE 5 is a diagrammatic horizontal plan of the embodiment disclosedwherein a. plus curve is generated;

FIGURE 6 is a diagrammatic elevation of the improvement shown in FIGURES4 and 5; and

FIGURE 7 is a horizontal cross section through the abrading tool.

The advancement of this invention can best be understood when it isanalyzed together with the operation of a prior art device. One suchprior art device is shown ICC in FIGURES 1, 2 and 3. Such a lensgenerator is conveniently divided into two major assemblies; namely anabrading tool support assembly 12 and the work or lens blank holderassembly 14. The assembly 14 is only disclosed in FIGURE 1 since it isconventional in operation and design and is eliminated from the otherdrawing for purposes of clarity. A lent blank L is supported by assembly14 in the path of the grinding sweep of the abrading tool T. Theassembly includes means well known to the art for moving the blank Ltoward and away from the assembly 12 along the longitudinal length of asupporting base 18 such as by tracks 19. (Again the tracks are onlyshown in FIGURE 1.)

The sweep assembly 12 of this prior art device consists of fourprincipal elements: a base slide 22, a generally lower deck member 24,an upper pie-shaped deck 25 and a workholder or quill 26 which isslidably received on the member 25 via the slide tracks 28 and 29between the adjustable abutments 30 and 32.

As best seen in FIGURE 3, the grinding assembly 12 is pivotallysupported about a trunnion 34 of base 18 about a fixed axis 36. Theposition of axis 36 remains constant throughout all grinding sweeps. Theupper surface of base slide 22 is equipped with tracks 40 which slidablyreceive the lower deck member 24. The deck member 24 is provided at itsend toward the work piece with an upstanding pin 42. The horizontalrelationship, distance D, between pin 42 and axis 36 can therefor bevaried by moving lower deck 24 along base slide 22.

Pivotally disposed about pin 42 is the upper desk 25. The upper deck ismovable about pin 42 in order to vary the angle of the abrading toolduring the generating sweep in order to determine cross curve. Note(FIGURE 7) that the edge of the abrading tool is located precisely overthe central axis 41 of pin 42. As is conventional, the base curve of theprescription is set by locating the pin 42 with respect to axis 36 andthe cross-curve is determined by selecting the angle between the quilland the slide 22. See the U.S. patent to Suddarth et al. 2,556,604issued .Tune 12, 1951.

As is conventional in machines of this type, there are means to locklower deck 24 with respect to the base slide 22 and to lock the upperdeck 25 with resect to the lower deck 24 when the proper settings havebeen made. As is well known to the art, the grinding sweep occurs as theassembly 12 is rotated about axis 36.

For minus cuttings, the grinding sweep occurs to the right of axis 36(as viewed from the top as seen in FIG- URE 1). As the assembly 12 isrotated about the axis 36 in the direction indicated 'by the arrow 50,as can be seen in FIGURE l, the grinding edge 52 of the abrading cup Tforms the surface on the lens blank L. As previously mentioned, the basecurve of the lens depends on the distance D set into the machine betweenthe pivot axis 36 and the axis of pin 42. As will also be wellunderstood to those skilled in the art, the cross-curve or verticalcomponent of the prescriptive lens surface is determined by the angle 54made between the axis of the abrading tool and the longitudinal axis ofthe base slide. This setting is made by swinging the deck 25 withrespect to the deck 24 and locking them into position. The lower deck 24is equipped with an arcuate slide portion 27 to receive the upper deck25.

In the event it is desired to form a convex or plus curve, the abradingsweep must occur to the left of axis 36 (FIGURE 2). As seen in FIGURE 2,both the work piece L and the deck 24 are moved an appropriate amount tothe right of axis A for a sweep of this type. See the dotted lineposition in FIGURE 3. In order to obtain the proper relationship betweenparts, the quill 26 is moved exactly one abrading tool width between thestops 30` and 32 so that the edge 53 of the abrading tool will sweepover the lens blank L as the assembly 12 is moved in the direction ofarrow 50. Again, the distance between the grinding edge 53 and the mainpivot 36 will determine the base curve and the angle between thelongitudinal axis of the abrading tool and the longitudinal axis of thebase determine the cross curve.

From the above, it can be seen that the quill moved exactly one abradingtool width in converting from a minus curve to a plus curve sweep.Since, in kgenerators of this type, the grinding edge of the abradingtool must be closely controlled with respect to the pin 42, it isessential that the edge 53 assumes the same relationship with the axis42 as the edge 52 has with this axis. Therefore, the movement of thequill 26 between the stops 30 and 32 is critical.

The essence of the present invention is providing a structure wherebythe abrading edge 52. maintains its relationship With pin 42 whetherplus or minus curves are generated. The above is accomplished byrotatably mounting a second upper deck 60 about the pin 42 and mountingthe quill 26 to this upper deck 60. All other elements of thecombination remain the same except that slides 28-29 and stops 30 areeliminated. In their place, a pair of stops 62 and 64, against which theupper deck 60 abuts are provided. In the device, FIGURES 4-6, the edge52 always remains disposed over the pin 42. Referring now to FIGURE 4where the assembly is disposed for minus cutting, the edge 52 willtraverse the lens blank along its sweep as the assembly 12 is moved inthe grinding direction indicated by the arrow 70. Again the base curveis determined by the distance between the axis 36 and the axis of pin 42and the cross-curve is determined by the relationship of the axis of theabrading tool and the axis of the lens blank. As seen in FIGURE 5, theangular disposition of the abrading tool T is changed with respect tothe lens blank while rotating the upper deck 60 with respect to thelower ldeck 24. With this arrangement, note that a minus curve is groundwhen the assembly 12 is rotated clockwise as indicated by the arrow 20and that the plus Curves are ground when the assembly 12 is rotated inthe counter-clockwise direction as indicated by the arrow J72. As aresult of this, the operator is fully aware of whether he is cutting aconvex or a concave surface by the direction of sweep.

Although the adjustment stops 62 and 64 are necessitated in the devicefor grinding accurate lenses, their function is not so critical as theprecise placement of the abrading edge 52 over the axis of the pin 42.Therefor, accurate lenses can be ground in a lens generator of the typedescribed even though the lens generator is adapted for quick and easyconvertibility between minus and plus curves.

What has been set forth above is intended primarily as exemplary toenable those skilled inthe art in the practice of the invention and itshould therefore be understood that, within the scope of the appendedclaim, the invention may be practiced in other ways than as specificallydescribed.

What is new and therefore desired to be protected by Letters Patent ofthe United States is:

1. A lens generator comprising an elongated base having a generallyhorizontal upper surface, a work holder slidably and adjustablysupported on said base for movement along the longitudinal axis of saidbase, a cup shaped abrading tool having an annular grinding edgedisposed in a vertical plane and said edge having a uniformsemi-circular cross-section throughout its annular length, a verticalpivot pin disposed below said tool having a center axis intersecting oneportion of said edge at the center of a cross-section dened by ahorizontal plane which also intersects the axis of rotation of saidabrading tool, a sweep assembly for supporting said tool, said assemblyincluding a base slide rotatably supported on said base about firstvertical axis which intersects said longitudinal axis of said base, alower deck carrying said pivot pin, rst means mounting said lower deckfor slidable movement with respect to said base slide whereby thedistance between said pivot pin and said iirst vertical axis isadjustable, a first upper deck pivotally mounted on said lower deckabout said pin, a second upper deck carrying said abrading tool andpivotally mounted on said first upper deck about said pin.

References Cited UNITED STATES PATENTS 1,325,789 12/1919 Johnson 51-33.13,117,396 1/1964 Dalton 51-33 2,806,327 9/1957 Coburn 5l-55 X 2,556,6046/1951 Suddarth et al. 51-55 JAMES L. I ONES, JR., Primary Examiner.

U.S. C1. X.R. 51-124

